A method for purging a governing system in a steam turbine

Abstract

The application discloses a flushing method for a speed regulating system in a steam turbine and relates to the technical field of steam turbine flushing. The flushing method for the speed regulating system in the steam turbine comprises the following steps: pipeline independent pulsating flushing, oil cylinder internal pulsating flushing and ultrasonic wave cooperative flushing, intelligent self-determination of a flushing end point, and flushing system recovery. The initial contamination degree data of oil liquid in a pipeline of the speed regulating system is acquired through an online particle size sensor, and variable flow pulsating waveform parameters are automatically generated by an intelligent control terminal based on the initial contamination degree data, so that the oil liquid flow rate in the pipeline is periodically alternated between a high-speed section and a low-speed section. The high-speed section flow rate is 2 to 5 times the normal operation flow rate of the system, and the pipe wall shear stress is much higher than that in the normal operation condition, so that the attached welding slag, rust and oxide skin on the pipe wall can be effectively stripped. The low-speed section keeps the pollutants suspended and carried and provides immersion and penetration time for the next cycle, so that the full-process automation of the pulsating flushing based on data driving is realized.

Description

Technical Field

[0001] This invention relates to the field of steam turbine flushing technology, and more particularly to a flushing method for the speed control system in a steam turbine. Background Technology

[0002] The turbine speed control system is a core component of the turbine generator set control system. Its working medium is triaryl phosphate fire-resistant oil, and the system contains precision hydraulic components such as servo valves and hydraulic actuators. After a major overhaul or commissioning of a new unit, contaminants such as welding slag, rust, scale, and paint film inevitably remain inside the pipelines and equipment. These must be thoroughly removed through oil circulation flushing to ensure the safe and stable operation of the unit.

[0003] Currently, the flushing of turbine speed control systems mainly adopts a constant flow circulation flushing method. Flushing medium is supplied to the pipeline at a constant pressure and flow rate, relying on the oil flow to wash away contaminants adhering to the pipe walls. The contaminants are then trapped by filters on the return oil pipeline. During the flushing process, operators periodically take samples from the return oil pipeline for testing, and determine whether the cleanliness requirements have been met based on the test results. For stubborn varnish films formed over long-term operation, the emergency shutdown system or hydraulic actuator is typically removed offline, ultrasonically cleaned separately, and then reinstalled.

[0004] Existing flushing methods have the following shortcomings: First, under constant flow flushing, the oil flow rate in the pipeline is relatively stable, and the shear stress on the pipe wall is limited, making it difficult to effectively remove stubborn deposits such as welding slag, oxide scale, and paint film that have a high bonding strength with the pipe wall; Second, ultrasonic cleaning is all offline immersion type and cannot be coordinated with online oil circulation flushing; Third, the determination of the flushing endpoint relies on manual timed sampling and testing, lacking an automated decision-making mechanism based on real-time oil quality data; Fourth, the flushing parameters are all preset by the operator and cannot be dynamically adjusted according to the actual degree of contamination in the pipeline.

[0005] In summary, existing flushing methods for steam turbine speed control systems have significant shortcomings in terms of removing stubborn deposits, automation of the flushing process, and intelligent determination of the flushing endpoint, resulting in low flushing efficiency and unstable flushing quality. Therefore, there is an urgent need for a flushing method for steam turbine speed control systems that can achieve online coordination of pulsed flushing and ultrasonic flushing, and based on data-driven intelligent decision-making. Summary of the Invention

[0006] This invention proposes a flushing method for the speed control system in a steam turbine that enables online coordination of pulsed flushing and ultrasonic flushing, and data-driven intelligent decision-making. This method addresses the significant shortcomings of existing flushing methods for steam turbine speed control systems in terms of the ability to remove stubborn deposits, the degree of automation in the flushing process, and the intelligent determination of the flushing endpoint, which leads to low flushing efficiency and unstable flushing quality.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A flushing method for a speed regulating system in a steam turbine includes the following steps: Independent Pulsating Flushing of Pipelines: Initial contamination data of the oil in the pipeline of the speed regulation system is obtained through an online particle size sensor. Based on the initial contamination data, the intelligent control terminal automatically generates variable flow pulsating waveform parameters and starts a high-flow flushing oil pump to supply flushing medium to the pipeline of the speed regulation system. This causes the oil flow rate in the pipeline to alternate periodically between high-speed and low-speed sections, forming an alternating flushing state of high-speed stripping and low-speed wetting in the pipeline. The flushing flow rate in the high-speed section is 2 to 5 times the normal operating flow rate of the system, and the flushing flow rate in the low-speed section is 0.3 to 0.8 times the normal operating flow rate of the system. Hydraulic actuator cylinder internal pulse flushing and ultrasonic synergistic flushing: After the pipeline independent pulse flushing meets the standard, the intelligent control terminal automatically switches the flushing mode to cylinder flushing, adjusts the pulse waveform parameters, and simultaneously starts the ultrasonic transducers installed on the oil supply and return main pipes. The cavitation effect generated by the ultrasonic waves in the flushing oil works synergistically with the pulse flushing oil flow to flush the inner wall of the hydraulic actuator cylinder and the piston gap. The ultrasonic transducers are fixed to the outer wall of the pipeline by clamping and do not intervene in the internal medium of the pipeline. Intelligent self-judgment of flushing endpoint: During the flushing process, the online particle size sensor acquires the solid particle contamination data in the return oil in real time. The intelligent control terminal automatically determines the flushing endpoint based on the convergence trend of the contamination reduction curve. When the contamination reduction rate is lower than the preset convergence threshold for a consecutive preset statistical window and the current contamination level meets the preset cleanliness standard, the flushing is automatically judged to meet the standard and the flushing process is stopped. Flushing system restoration: After the flushing meets the standards and the machine automatically stops, remove the temporary flushing device and restore the speed control system to normal operation.

[0008] As a preferred technical solution of the present invention, in the independent pulsating flushing of the pipeline, the strategy of the intelligent control terminal to automatically generate pulsating flushing parameters based on the initial contamination parameters is as follows: the more severe the contamination, the higher the peak flow rate, the lower the pulsation frequency, and the longer the high-speed segment duration; after the contamination decreases, the intelligent control terminal automatically reduces the peak flow rate and narrows the pulsation frequency range to achieve dynamic adaptive adjustment of the flushing parameters.

[0009] As a preferred technical solution of the present invention, in the independent pulsating flushing of the pipeline, for the severely contaminated condition with an initial contamination level of NAS12, the pulsating parameters automatically generated by the intelligent control terminal are as follows: the pulsating waveform type is square wave, the pulsating frequency is 0.5Hz, the high-speed section flow rate is 360L / min, the low-speed section flow rate is 60L / min; the pipeline Reynolds number is greater than 7500 at an oil temperature of 45℃, and the pipe wall shear stress is 40 times that of the normal operating condition.

[0010] As a preferred embodiment of the present invention, in the combined pulse flushing and ultrasonic flushing of the internal pulsation flushing of the hydraulic cylinder, the intelligent control terminal automatically adjusts the pulsation parameters to: square wave frequency 0.2Hz, high-speed segment lasting 3 seconds, low-speed segment lasting 2 seconds, high-speed segment peak flow rate maintained at 360L / min, and low-speed segment valley flow rate reduced to 40L / min after the independent pulse flushing of the pipeline meets the standard; the automatic switching of the flushing mode is completed automatically after the intelligent control terminal confirms that the temporary flushing device at each hydraulic cylinder has been installed.

[0011] As a preferred embodiment of the present invention, the resonant frequency of the ultrasonic transducer is 28kHz, which belongs to the low-frequency ultrasonic cleaning frequency band of 20 to 50kHz; a set of transducers is arranged on each of the oil supply header and the oil return header, and each set consists of 4 clamp-type piezoelectric transducers with a rated power of 1200W, evenly distributed at 90-degree circumferential intervals at the same cross-sectional position of the pipeline, and tightly attached to the outer wall of the pipeline by coupling agent; the output power of the transducer is set to 75% of the rated power, and the total output power is 7200W.

[0012] As a preferred technical solution of the present invention, the cavitation effect of the ultrasound in the oil is manifested as follows: the oil alternately generates a positive pressure phase and a negative pressure phase under the action of alternating ultrasonic pressure. During the negative pressure phase, cavitation bubbles are formed in the oil and grow rapidly. During the positive pressure phase, the cavitation bubbles are rapidly compressed and collapsed, instantly generating impact pressure and micro-jet, which directly act on the paint film and oxides attached to the inner wall of the pipeline and the inner wall of the hydraulic cylinder of the hydraulic actuator. The pulse flushing provides high-speed scouring and contaminant carrying at the macro level, and the ultrasonic cavitation provides concentrated impact stripping at the micro level. The two work synergistically in the same flushing cycle.

[0013] As a preferred technical solution of the present invention, in the intelligent self-judgment of the flushing endpoint, the intelligent control terminal uses each minute as a statistical window, takes the average value of two NAS level data points within the window as the representative pollution level, calculates the moving average value and the rate of decrease of NAS level within each consecutive 30 minutes, and the statistical window of each consecutive 30 minutes contains 60 particle size sampling data points; when the rate of decrease is lower than 0.2 level / 30 minutes for two consecutive 30-minute windows, and all NAS level sampling values ​​in the current window are not higher than NAS5 level, the flushing is automatically judged to meet the standard and the flushing process is stopped.

[0014] As a preferred technical solution of the present invention, the independent pulse flushing of the pipeline and the pulse flushing inside the hydraulic cylinder of the hydraulic actuator, combined with ultrasonic flushing, adopt a three-stage series filtration structure: the first stage is a 100μm stainless steel mesh coarse filter, the second stage is a 10μm precision filter element filter, and the third stage is a 3μm ultra-precision filter element filter, so as to achieve gradient interception of pollutants with different particle sizes; differential pressure sensors are installed at both ends of each filter, and the intelligent control terminal automatically alarms when the filter element is blocked.

[0015] As a preferred embodiment of the present invention, the flushing medium is selected as ISO VG46 grade triaryl phosphate fire-resistant oil, with a kinematic viscosity of 43.4 to 46.0 mm² / s at 40°C, a density of 1.13 to 1.17 g / cm³, an acid value not exceeding 0.05 mg KOH / g, and a particulate contamination level not exceeding NAS6. The oil is preheated to 45±5°C, within which its fluidity is significantly enhanced and will not cause oil deterioration.

[0016] As a preferred technical solution of the present invention, during the flushing process, the pressure of the main oil supply pipe is monitored in real time by a pressure transmitter. An abnormal increase in pressure indicates that there may be a blockage in the pipeline. The instantaneous flow rate is monitored in real time by a turbine flow meter. An abnormal decrease in flow rate indicates that there is an abnormality in the oil pump or pipeline. Data from each sensor is collected in real time and displayed on the touch screen interface, including ISO code and NAS level trend curves, oil supply pressure waveform, instantaneous flow waveform, and pressure difference trend lines of each filter.

[0017] The present invention has the following advantages: This invention acquires initial contamination data of the oil in the pipeline of a speed-regulating system using an online particle size sensor. Based on this initial contamination data, an intelligent control terminal automatically generates variable flow pulsating waveform parameters, causing the oil flow rate in the pipeline to alternate periodically between high-speed and low-speed sections. The flow rate in the high-speed section is 2 to 5 times that of the normal operating flow rate, and the shear stress on the pipe wall is much higher than that under normal operating conditions, effectively removing welding slag, rust, and oxide scale attached to the pipe wall. In the low-speed section, contaminants are kept suspended and carried, providing time for wetting and penetration in the next cycle. This invention achieves full automation of the flushing process based on data-driven automatic generation of flushing parameters and pulsating flushing, overcoming the problems of insufficient flushing force and reliance on manual parameter presets in traditional constant flow flushing.

[0018] This invention integrates a 28kHz low-frequency ultrasonic transducer into the outer wall of the oil supply and return manifolds during pulsed flushing and ultrasonic synergistic flushing inside the hydraulic cylinder of a hydraulic actuator. It utilizes the cavitation effect generated by ultrasound in the oil, combined with the periodic pulsed flushing oil flow. Specifically, the negative pressure phase forms and rapidly grows cavitation bubbles, while the positive pressure phase sees the cavitation bubbles collapse, generating instantaneous high-pressure impacts and micro-jet streams. The pulsed flow provides macroscopic scouring and contaminant carrying capacity, while the ultrasound provides microscopic impact and peeling capacity. This effectively removes stubborn deposits such as paint and oxide scale that are difficult to remove using traditional methods. It achieves online flushing with synergistic pulsed flushing and ultrasound, overcoming the problem that existing ultrasonic cleaning methods are all offline immersion-type and cannot be coordinated with online oil circulation flushing.

[0019] This invention acquires real-time solid particle contamination data in return oil using an online particle size sensor. The intelligent control terminal automatically determines the flushing endpoint based on the convergence trend of the contamination decrease curve. When the decrease rate is below the preset convergence threshold for several consecutive preset statistical windows and the current contamination level meets the preset cleanliness standard, the flushing is automatically deemed satisfactory and the flushing process is stopped. This avoids the problem of insufficient or excessive flushing caused by relying on human experience, and realizes data-driven intelligent decision-making at the flushing endpoint, ensuring stable and controllable flushing quality.

[0020] This invention automatically generates pulse flushing parameters based on initial contamination parameters through an intelligent control terminal, and automatically reduces peak flow and narrows the pulse frequency range as contamination decreases, achieving dynamic adaptive adjustment of flushing parameters. This results in higher peak flow, lower pulse frequency, and longer high-speed duration when contamination is more severe. After contamination decreases, the parameters are automatically optimized to avoid over-flushing, thus balancing flushing efficiency with the safety of pipelines and seals. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only schematic diagrams of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort. Figure 1 This is a schematic flowchart of a flushing method for a speed control system in a steam turbine, as used in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] Example 1: A flushing method for the speed control system in a steam turbine, such as... Figure 1 As shown, it includes the following steps: This embodiment provides a flushing method for the speed control system in a steam turbine, applied to the post-maintenance flushing operation of the speed control system of a 600MW steam turbine unit. The speed control system uses high-pressure fire-resistant oil as the working medium, the normal operating flow rate of the system is 120L / min, the pipeline material is stainless steel, and the number of hydraulic cylinders is 8.

[0024] In this embodiment, before the flushing operation begins, the temporary flushing device is first installed. The temporary flushing device includes: a high-flow-rate flushing oil pump, a three-stage series filtration unit, an online particle size sensor, a pressure transmitter, a turbine flow meter, an ultrasonic transducer assembly, and an intelligent control terminal. The high-flow-rate flushing oil pump has a rated flow rate of 600 L / min, meeting the flushing flow requirements of the high-speed section. The three-stage series filtration unit includes a 100 μm stainless steel mesh coarse filter, a 10 μm precision filter element, and a 3 μm ultra-precision filter element, with differential pressure sensors installed at both ends of each filter stage. The online particle size sensor is installed on the return oil header to monitor the return oil contamination level in real time. The pressure transmitter is installed on the supply oil header, and the turbine flow meter is installed between the supply oil header and the oil pump outlet. The ultrasonic transducer assembly includes a supply oil header transducer assembly and a return oil header transducer assembly. Each assembly consists of four clamp-on piezoelectric transducers with a rated power of 1200 W, evenly distributed at 90-degree circumferential intervals at the same cross-sectional position in the pipeline, and tightly bonded to the outer wall of the pipeline using a coupling agent.

[0025] The flushing medium is ISO VG46 grade triaryl phosphate fire-resistant oil, with a kinematic viscosity of 43.4 mm² / s, a density of 1.15 g / cm³, an acid value of 0.03 mg KOH / g, and a particulate contamination level of NAS5 at 40°C. Before flushing, the oil is preheated to 45°C and maintained at 45±5°C using a temperature control system.

[0026] Step 1: Independent pulse flushing of pipelines; The intelligent control terminal is activated, and the initial contamination level of the oil in the speed control system pipeline is obtained through an online particle size sensor installed on the return oil header. The initial contamination level is detected to be NAS12, indicating a severely contaminated operating condition.

[0027] The intelligent control terminal automatically generates variable flow rate pulsating waveform parameters based on the initial contamination level data. According to a preset strategy, the more severe the contamination, the higher the peak flow rate, the lower the pulsation frequency, and the longer the high-speed segment duration. For the severe contamination condition of NAS12 level, the pulsation parameters automatically generated by the intelligent control terminal are as follows: the pulsation waveform type is a square wave, the pulsation frequency is 0.5Hz, the high-speed segment flow rate is 360L / min (3 times the normal operating flow rate of the system), and the low-speed segment flow rate is 60L / min (0.5 times the normal operating flow rate of the system). The high-speed segment lasts for 1 second, and the low-speed segment lasts for 1 second, forming a periodic alternating flushing state.

[0028] The high-flow-rate flushing oil pump is started to supply flushing medium to the speed-regulating system pipeline. In the high-speed section, the oil flows at a high speed of 360L / min, and at an oil temperature of 45℃, the pipeline Reynolds number is greater than 7500, and the shear stress of the pipe wall reaches 40 times that of normal operating conditions, effectively peeling off the paint film and oxides adhering to the inner wall of the pipeline; in the low-speed section, the oil flows at a low speed of 60L / min, allowing the flushing medium to fully wet the inner wall of the pipeline, softening residual contaminants and creating conditions for the high-speed stripping in the next cycle.

[0029] During the flushing process, the intelligent control terminal receives real-time contamination data from the online particle size sensor. As flushing progresses, the contamination level in the pipeline gradually decreases. When the contamination level drops to NAS8, the intelligent control terminal automatically adjusts the pulsation parameters: reducing the peak flow rate to 300 L / min, increasing the pulsation frequency to 0.8 Hz, and shortening the high-speed segment duration to 0.8 seconds, achieving dynamic adaptive adjustment of flushing parameters and avoiding energy waste caused by over-flushing.

[0030] During the independent pulsed flushing process, the flushing medium passes through a three-stage cascaded filtration structure: the first stage is a 100μm stainless steel mesh coarse filter to remove large particles; the second stage is a 10μm precision filter to remove medium-sized particles; and the third stage is a 3μm ultra-precision filter to remove fine particles. Differential pressure sensors at both ends of each filter stage monitor the filter element clogging status in real time. When the differential pressure of any stage filter exceeds a preset threshold, the intelligent control terminal automatically alarms and prompts for filter element replacement.

[0031] Meanwhile, the pressure transmitter monitors the main oil supply line pressure in real time, and the turbine flow meter monitors the instantaneous flow rate in real time. If the pressure rises abnormally, it indicates a possible blockage in the pipeline; if the flow rate drops abnormally, it indicates a problem with the oil pump or pipeline. Data from each sensor is collected in real time and displayed on the touchscreen interface, including ISO code and NAS level trend curves, oil supply pressure waveforms, instantaneous flow waveforms, and differential pressure trend lines for each filter level, allowing operators to monitor the flushing status in real time.

[0032] Step 2: Combined pulsating flushing and ultrasonic flushing inside the hydraulic cylinder of the hydraulic actuator; Once the independent pulse flushing of the pipeline meets the standard, that is, when the contamination level in the pipeline stabilizes below NAS6 and the downward trend slows down significantly, the intelligent control terminal automatically switches the flushing mode to hydraulic cylinder flushing.

[0033] Before switching the flushing mode, the intelligent control terminal first confirms that the temporary flushing devices at each hydraulic actuator are installed in place. The temporary flushing devices include a temporary pipeline connecting the oil supply main pipe to the hydraulic actuator inlet, a temporary pipeline connecting the hydraulic actuator return port to the return main pipe, and corresponding quick-connect fittings. Once the installation is confirmed, the intelligent control terminal automatically performs the mode switch.

[0034] After mode switching, the intelligent control terminal adjusts the pulse waveform parameters as follows: square wave frequency 0.2Hz, high-speed segment lasting 3 seconds, low-speed segment lasting 2 seconds, high-speed segment peak flow rate maintained at 360L / min, and low-speed segment valley flow rate reduced to 40L / min. Compared to the pipeline flushing stage, the cylinder flushing stage reduces the pulse frequency, extends the duration of the high-speed segment, and increases the high-low speed flow difference to enhance the flushing effect on the inside of the hydraulic actuator cylinder and piston clearance.

[0035] Simultaneously, the intelligent control terminal activates the ultrasonic transducers installed on the oil supply and return main pipes. The resonant frequency of the ultrasonic transducers is 28kHz, belonging to the low-frequency ultrasonic cleaning band of 20 to 50kHz. One set of transducers is arranged on each of the oil supply and return main pipes. Each set consists of four clamp-on piezoelectric transducers with a rated power of 1200W, evenly distributed at 90-degree circumferential intervals at the same cross-sectional position of the pipeline, and tightly bonded to the outer wall of the pipeline using a coupling agent. The transducer output power is set to 75% of the rated power, with a single set output power of 3600W and a total output power of 7200W for both sets.

[0036] Ultrasonic waves generate cavitation in oil: under the alternating sound pressure of ultrasound, the oil alternately generates positive and negative pressure phases. During the negative pressure phase, cavitation bubbles form and grow rapidly in the oil; during the positive pressure phase, the cavitation bubbles are rapidly compressed and collapse, instantaneously generating localized high temperature and pressure and microjets. The impact pressure of these microjets can reach hundreds or even thousands of atmospheres, directly acting on the paint film and oxides adhering to the inner walls of pipelines and hydraulic cylinders, achieving concentrated impact peeling at the microscopic level.

[0037] Pulsating flushing provides high-speed scouring and contaminant removal at the macroscopic level: in the high-speed phase, a large flow of oil passes through the hydraulic actuator cylinder at high speed, generating strong shearing and scouring against the inner wall and rapidly carrying away the dislodged contaminants; in the low-speed phase, the oil flow rate decreases, allowing the micro-jet generated by the ultrasonic cavitation effect sufficient time to act on the wall surface, while avoiding excessive disturbance of the cavitation bubbles by the high-speed flow. Both work synergistically in the same flushing cycle, with macroscopic scouring and microscopic dislodging mutually promoting each other, significantly improving the cleaning effect on the complex internal structure of the hydraulic actuator cylinder and piston clearances.

[0038] Step 3: Intelligent self-judgment of the rinsing endpoint During the hydraulic cylinder flushing stage of the hydraulic actuator, the online particle size sensor acquires real-time data on the solid particle contamination level in the return oil. The intelligent control terminal uses a minute-by-minute statistical window and calculates the average value of two NAS-level data points within that window as the representative contamination level.

[0039] The intelligent control terminal calculates the moving average and rate of decline of the NAS level over every 30 consecutive minutes. The 30-minute statistical window contains 60 granular sampling data points (2 data points per minute). For each spatial unit, within the current time slice, its behavioral intensity value is acquired, and the difference between its behavioral intensity values ​​and those of all its neighboring spatial units is calculated.

[0040] The specific judgment logic is as follows: when the rate of decline is below 0.2 / 30 minutes for two consecutive 30-minute windows, and all NAS level sampling values ​​in the current window are not higher than NAS5 level, the flushing is automatically judged to meet the standard and the flushing process is stopped.

[0041] In this embodiment, after 6 hours of cylinder flushing, the intelligent control terminal detected that: within the first 30-minute window, the NAS level decreased from NAS5.2 to NAS5.0, at a rate of 0.2 levels per 30 minutes; within the second 30-minute window, the NAS level remained at NAS5.0, at a rate of 0 levels per 30 minutes. All NAS level samples within the current window were not higher than NAS5. Meeting the flushing endpoint determination criteria, the intelligent control terminal automatically determined that the flushing had met the standards and sent a shutdown command to the high-flow-rate flushing oil pump and ultrasonic transducer, stopping the flushing process.

[0042] Step 4: Restore the flushing system After the rinsing process is complete and the machine automatically shuts down, the operator should follow these steps to restore the speed control system to normal operation: First, shut down the high-flow flushing oil pump to cut off the flushing medium supply. Second, sequentially shut down the ultrasonic transducer groups on the oil supply header and return header and disconnect their power supply. Then, remove the temporary flushing devices at each hydraulic actuator and restore the normal connection between the hydraulic actuator and the system pipeline. Next, disconnect the three-stage series filter unit from the flushing circuit and restore the system to normal operation. Finally, fill and vent the speed control system with oil, check for leaks at all connections, and then switch the system to normal operation mode.

[0043] After the recovery was completed, the system oil contamination level was detected again by an online particle size sensor and confirmed to have reached NAS5 level, which meets the cleanliness requirements for normal operation of the speed control system. The flushing operation was then completed.

[0044] Example 2: This example provides a flushing method for the speed control system in a steam turbine. The difference from Example 1 lies in the adaptive adjustment strategy of the initial contamination level and the corresponding pulsating flushing parameters.

[0045] In this embodiment, the speed control system of a 300MW steam turbine unit underwent maintenance after long-term operation. The initial pollution level was measured as NAS9, which is a medium pollution condition.

[0046] Based on the initial pollution level data of NAS9, the intelligent control terminal automatically generates the following pulsation parameters: the pulsation waveform type is square wave, the pulsation frequency is 1.0Hz, the high-speed flow rate is 240L / min (twice the normal operating flow rate of the system), and the low-speed flow rate is 80L / min (0.67 times the normal operating flow rate of the system). The high-speed segment lasts for 0.5 seconds, and the low-speed segment lasts for 0.5 seconds.

[0047] As flushing proceeds, when the contamination level decreases to NAS6, the intelligent control terminal automatically adjusts the pulsation parameters: reducing the peak flow rate to 180 L / min, increasing the pulsation frequency to 1.5 Hz, and shortening the high-speed phase duration to 0.4 seconds. When the contamination level further decreases to NAS5, the pulsation parameters are adjusted again: the peak flow rate is reduced to 150 L / min, and the pulsation frequency is increased to 2.0 Hz.

[0048] The remaining rinsing steps are the same as in Example 1. This example demonstrates that the intelligent control terminal can automatically generate suitable pulsed rinsing parameters based on the initial contamination level parameters, and dynamically and adaptively adjust them according to changes in contamination level during the rinsing process, achieving efficient rinsing under different contamination levels.

[0049] Example 3: This example provides a flushing method for the speed control system in a steam turbine. The difference between this example and Example 1 lies in the arrangement and power configuration of the ultrasonic transducer.

[0050] In this embodiment, a set of transducers is arranged on both the supply and return oil headers. Each set consists of six clamp-on piezoelectric transducers with a rated power of 800W, evenly distributed at 60-degree circumferential intervals at the same cross-sectional position of the pipeline. The resonant frequency of the transducers is 40kHz, and the output power is set to 80% of the rated power. The output power of a single set is 3840W, and the total output power of the two sets is 7680W.

[0051] The higher resonant frequency (40kHz) results in smaller cavitation bubble size and finer microjet, making it suitable for cleaning precision servo valves and small pipelines; the greater number of transducers (6 per group) and the smaller circumferential spacing (60 degrees) make the ultrasonic energy more evenly distributed around the pipeline, avoiding pipeline damage caused by local energy concentration.

[0052] The remaining rinsing steps are the same as in Example 1. This example demonstrates that the number and power configuration of the ultrasonic transducers can be flexibly adjusted according to the pipeline size and cleaning requirements. Within the low-frequency ultrasonic cleaning band of 20 to 50 kHz, different resonant frequencies are suitable for different cleaning scenarios.

[0053] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flushing method for a speed regulating system in a steam turbine, characterized in that, Includes the following steps: Independent Pulsating Flushing of Pipelines: Initial contamination data of the oil in the pipeline of the speed regulation system is obtained through an online particle size sensor. Based on the initial contamination data, the intelligent control terminal automatically generates variable flow pulsating waveform parameters and starts a high-flow flushing oil pump to supply flushing medium to the pipeline of the speed regulation system. This causes the oil flow rate in the pipeline to alternate periodically between high-speed and low-speed sections, forming an alternating flushing state of high-speed stripping and low-speed wetting in the pipeline. The flushing flow rate in the high-speed section is 2 to 5 times the normal operating flow rate of the system, and the flushing flow rate in the low-speed section is 0.3 to 0.8 times the normal operating flow rate of the system. Hydraulic actuator cylinder internal pulse flushing and ultrasonic synergistic flushing: After the pipeline independent pulse flushing meets the standard, the intelligent control terminal automatically switches the flushing mode to cylinder flushing, adjusts the pulse waveform parameters, and simultaneously starts the ultrasonic transducers installed on the oil supply and return main pipes. The cavitation effect generated by the ultrasonic waves in the flushing oil works synergistically with the pulse flushing oil flow to flush the inner wall of the hydraulic actuator cylinder and the piston gap. The ultrasonic transducers are fixed to the outer wall of the pipeline by clamping and do not intervene in the internal medium of the pipeline. Intelligent self-judgment of flushing endpoint: During the flushing process, the online particle size sensor acquires the solid particle contamination data in the return oil in real time. The intelligent control terminal automatically determines the flushing endpoint based on the convergence trend of the contamination reduction curve. When the contamination reduction rate is lower than the preset convergence threshold for a consecutive preset statistical window and the current contamination level meets the preset cleanliness standard, the flushing is automatically judged to meet the standard and the flushing process is stopped. Flushing system restoration: After the flushing meets the standards and the machine automatically stops, remove the temporary flushing device and restore the speed control system to normal operation.

2. The flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, In the independent pulse flushing of the pipeline, the strategy of the intelligent control terminal to automatically generate pulse flushing parameters based on the initial contamination parameters is as follows: the more severe the contamination, the higher the peak flow rate, the lower the pulse frequency, and the longer the high-speed section lasts; after the contamination decreases, the intelligent control terminal automatically reduces the peak flow rate and narrows the pulse frequency range to achieve dynamic adaptive adjustment of flushing parameters.

3. The flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, In the independent pulse flushing of the pipeline, for the severely contaminated condition with an initial contamination level of NAS12, the pulse parameters automatically generated by the intelligent control terminal are as follows: the pulse waveform type is square wave, the pulse frequency is 0.5Hz, the high-speed section flow rate is 360L / min, the low-speed section flow rate is 60L / min; the pipeline Reynolds number is greater than 7500 at an oil temperature of 45℃, and the pipe wall shear stress is 40 times that of the normal operating condition.

4. The flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, During the combined pulsed flushing and ultrasonic flushing of the hydraulic cylinder, the intelligent control terminal automatically adjusts the pulse parameters to the following after the independent pulsed flushing of the pipeline meets the standard: square wave frequency 0.2Hz, high speed section lasting 3 seconds, low speed section lasting 2 seconds, high speed section peak flow rate maintained at 360L / min, and low speed section valley flow rate reduced to 40L / min; the flushing mode is automatically switched by the intelligent control terminal after confirming that the temporary flushing device at each hydraulic cylinder has been installed.

5. The flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, The resonant frequency of the ultrasonic transducer is 28kHz, which belongs to the low-frequency ultrasonic cleaning frequency band of 20 to 50kHz. A set of transducers is arranged on each of the oil supply header and the oil return header. Each set consists of four clamp-type piezoelectric transducers with a rated power of 1200W, evenly distributed at 90-degree circumferential intervals at the same cross-sectional position of the pipeline, and tightly attached to the outer wall of the pipeline with a coupling agent. The output power of the transducers is set to 75% of the rated power, and the total output power is 7200W.

6. The flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, The cavitation effect of ultrasound in oil is manifested as follows: under the action of alternating ultrasonic pressure, the oil alternately generates positive and negative pressure phases. During the negative pressure phase, cavitation bubbles are formed and grow rapidly in the oil. During the positive pressure phase, the cavitation bubbles are rapidly compressed and collapse, instantly generating impact pressure and micro-jet, which directly act on the paint film and oxides attached to the inner wall of the pipeline and the inner wall of the hydraulic cylinder. The pulse flushing provides high-speed scouring and contaminant carrying at the macro level, while the ultrasonic cavitation provides concentrated impact stripping at the micro level. The two work synergistically in the same flushing cycle.

7. The flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, In the intelligent self-judgment of the flushing endpoint, the intelligent control terminal uses each minute as a statistical window, takes the average value of two NAS level data points within the window as the representative pollution level, calculates the moving average value and the rate of decrease of NAS level within each consecutive 30 minutes, and the statistical window of each consecutive 30 minutes contains 60 particle size sampling data points; when the rate of decrease is lower than 0.2 level / 30 minutes for two consecutive 30-minute windows, and all NAS level sampling values ​​in the current window are not higher than NAS5 level, the flushing is automatically judged to meet the standard and the flushing process is stopped.

8. A flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, During the independent pulse flushing of the pipeline and the pulse flushing inside the hydraulic cylinder combined with ultrasonic flushing, a three-stage series filtration structure is adopted: the first stage is a 100μm stainless steel mesh coarse filter, the second stage is a 10μm precision filter element filter, and the third stage is a 3μm ultra-precision filter element filter, so as to achieve gradient interception of pollutants with different particle sizes; differential pressure sensors are installed at both ends of each filter, and the intelligent control terminal automatically alarms when the filter element is blocked.

9. A flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, The flushing medium is selected from ISO VG46 grade triaryl phosphate fire-resistant oil, with a kinematic viscosity of 43.4 to 46.0 mm² / s at 40°C, a density of 1.13 to 1.17 g / cm³, an acid value not exceeding 0.05 mg KOH / g, and a particulate contamination level not exceeding NAS6. The oil is preheated to 45±5°C, within which its fluidity is significantly enhanced and will not cause oil deterioration.

10. A flushing method for a speed regulating system in a steam turbine according to claim 1, characterized in that, During the flushing process, the pressure of the main oil supply pipe is monitored in real time by a pressure transmitter. An abnormal increase in pressure indicates that there may be a blockage in the pipeline. The instantaneous flow rate is monitored in real time by a turbine flow meter. An abnormal decrease in flow rate indicates that there is an abnormality in the oil pump or pipeline. Data from each sensor is collected in real time and displayed on the touchscreen interface, including ISO code and NAS level trend curves, oil supply pressure waveform, instantaneous flow waveform, and differential pressure trend lines for each filter level.

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